Every boat I have had uses this plug also. They say to put it in from the inside. Reason being is that it may come out if installed from the rear. I’ve never had that happen in 40 some years. Kim
Some boats have a sub-hull, between deck and hull.
It's filled with floatation/fuel tank, the deck bonds to hull several inches up the transom, and the lower cavity can only be drained from the outside , as shown above .
Cheers.
